Only add Tomcat connectors in start() method

Update TomcatEmbeddedServletContainer so that Connectors are removed
during initialization and re-added when the start() method is called.

This prevent protocol handlers from being bound then immediately
unbound. It also ensure that any additional connectors that may have
been added don't accidentally start to accept traffic (which could cause
potential deadlock issues).

Fixes gh-1212
Polish embedded tomcat classes

Extract some methods to aid readability.